I need to know if there's an "easy" way of keeping the OEM brightness switch instead of using the one that came with the gauges. There's a rocker switch to choose either green or blue and there's also the brightness rotary switch.

 

the brightness switch (for both) is probably just a potentiometer. both perform the same function but the resistance spectrum provided by both may be quite different. with a little though and research you may be able to make it work.

or you could just put it in and see if it works. but if there's any warranty with them say bye bye.

 

I know what you mean about the ugliness of it. Another quicker but simple way around it is using it but putting it into an empty switch spot on your dash (such as where the OEM fog light switch usually goes). I wish I had a pic to show of my car and my friends car I did but basically, I took the dimmer and color switch off the metal plate and thre that stupid thing away. Then I pulled out an empty cover off the dash and opened the correct size holes and installed my switches there. It turns out looking really good and professional.